It is known in the art that a liquid and gas can be separated by a separator formed from porous material having a "bubble pressure" in excess of a pressure differential across the separator. In such separators the liquid forms a film, with a rupture strength dependent on the physical properties of the liquid and the pore size of the separator, and the film cannot be broken at the operating pressure differential. The separator allows the liquid to flow from the higher pressure side to the lower pressure side while prohibiting the gas from entering the lower pressure region.
For example, U.S. Pat. No. 3,933,448 to Di Peri discloses a fuel reservoir, e.g., a fuel reservoir for aircraft, which contains fuel and undesirable gas bubbles. To ensure that only fuel exits the fuel reservoir, a liquid/gas separator comprising a mesh screen (250.times.1370 wires per inch) is employed at the fuel outlet. The fuel forms a film on the screen and the film allows liquid to pass through the mesh, but its surface tension prevents the passage of undesirable gas bubbles from the fuel reservoir.
U.S. Pat. No. 4,543,303 to Dantowitz et al. teaches a fuel cell battery apparatus which separates by-product water formed by the combination of hydrogen and oxygen gasses in each of the battery cells by means of a liquid/gas separator comprising porous discs of sintered niobium metal. The sintered niobium discs permit the flow of water but block the flow of gas at operating pressure because of the "bubble pressure" created by the surface tension of the water. In Dantowitz, the water is apparently urged into contact with the water/gas separator at the bottom of each battery cell by gravitational force.
U.S. Pat. No. 4,729,932 to McElroy also discloses a fuel cell battery in which water is separated from gas by a sintered metal separator, preferably sintered niobium. By inducing an approximate 3 pounds per square inch pressure differential across the water/gas separator, the liquid can readily pass through the separator while the gas remains on the high pressure side of the screen. McElroy states that such a system may ultimately be used in a zero gravity environment (apparently because of the pressure differential on opposite sides of the gas/water separator).
None of these patents, however, discloses a method and apparatus for separating liquid particles suspended in a liquid and gas mixture that is principally gas with relatively sparse liquid particles suspended within the gas.